The present invention relates to monitoring and altering an individual""s brain state. More particularly, the present invention is directed to the continuous real-time alteration of the brain state from a less desirable to a more desirable state through the use of multiple magnetic fields and a system monitoring the effect of the fields.
Most techniques for altering the brain state of a subject have concentrated on altering a measure of this state, i.e., the electroencephalogram (EEG) signal. The EEG is an electrical signal that is read on the surface of the skull which reflects the average activity of large groups of neurons and may, if properly interpreted, be indicative of the psychological state of the subject. EEG frequency bands are usually divided into (1) delta rhythms, having a frequency range of 1.5-3.5 Hz, (2) theta rhythms, having a frequency range of 3.5-7.5 Hz, (3) alpha rhythms, having a frequency range of 7.5-12.5 Hz, and (4) beta rhythms, having a frequency range of 12.5-20 Hz. Some frequencies above 20 Hz, such as the gamma range (around 40 Hz) have been implicated in various types of cognitive processing, although their role in indicating overall mood is still unclear. In general, the lower the mean frequency of the EEG signal, the lower the state of alertness, although many other factors may influence the interpretation of the EEG signal, including the location on the scalp of the EEG readings, the degree of synchronization between readings, and whether any psychological pathology is present.
Conventional EEG monitoring techniques have involved a skilled technician processing the raw signals by hand. A well-trained technician can often pinpoint abnormalities in such signals, although well-defined correlates between EEG signals and pathological brain states have only been made possible with the advent of quantitative EEG (QEEG) methods, in which the analog EEG signal is converted to a digital signal for further computational manipulation and analysis. Among the many features that QEEG can easily detect are precise power levels in different bandwidths, dynamic changes in bandwidths over time, and coherence between different parts of the brain. In conjunction with some theoretical assumptions, QEEG may also be used to provide a three-dimensional picture of brain activity. QEEG has also revealed a number of correlates between abnormal electrical activity and pathological states, including but not limited to, the states of dementia, schizophrenia, mood disorders, Attention Deficit Disorders (ADD), and alcohol and substance abuse (Hughes and John, 1999). In addition, it has been known for some time that relatively high activity in the alpha frequency band (8-13 Hz) in normal subjects is correlated with a feeling of relaxation.
These sorts of results have encouraged researchers to attempt to improve deficient or otherwise non-optimal mental states by attempting to manipulate the EEG. For example, depression has been correlated with an asymmetry in activity between the right and left prefrontal cortices, with greater activity in the right. To treat this condition, one would want to achieve an EEG signal which is more balanced between the hemispheres. Likewise, one might attempt an increase in the power level of the alpha band to increase relaxation.
One method for altering the brain signals is by biofeedback (see, e.g., U.S. Pat. No. 3,882,850), in which a patient is given a visual or auditory feedback proportional to the desired EEG signal. The patient attempts to increase the level of this feedback in order produce more of the desired signal. For example, in alpha feedback, the intensity of a sound may represent the degree of alpha present. By concentrating on raising the intensity of this sound, the patient thereby indirectly increases the intensity of the degree of alpha present, and presumably thereby increases her degree of relaxation. U.S. Pat. No. 5,280,793 describes a similar feedback mechanism for the correction of hemispheric asymmetry in activity levels associated with depression.
There are, however, limitations on what can be accomplished with this treatment paradigm. First and most fundamentally, the method can only work if it is conceivable that conscious effort can alter the brain in the desired way. The exact neural dynamics of biofeedback are unknown, but it is known that conscious effort is localized to specific areas of the brain, most likely those of the neocortex. If the right connections to other areas of the brain that are in need of change are not present, or are of the wrong sort, then biofeedback will not be possible. In short, the situation is one of a part of a dynamic system attempting to influence the state of the dynamic system as a whole, which may work in certain cases, but is less likely to work when large-scale, and/or long-term change must be effected. Secondly, biofeedback may be providing duplicate information. For example, presumably one either knows or can be taught to pay attention to how relaxed one is. In this case, audible feedback of the EEG signal may be simply a more complex method of achieving what can be done with simpler means.
For these reasons and others, researchers have turned to other means of altering the underlying brain state, while maintaining the basic mechanism of EEG feedback. For example, U.S. Pat. No. 5,495,853 uses photic stimulation delivered to the eyes through specially constructed glasses in order to alter the brain state. Meanwhile, the EEG signal is monitored. If the desired EEG signal is not being produced, then certain parameters of the stimulation, such as the frequency of the flashing of the lights, are changed until the desired signal is achieved.
This method, however, suffers from a similar problem to that of biofeedback. Visual stimulation is routed primarily through the optic tract to the thalamus and then to the occipital cortex, where most primary visual processing is accomplished. It is only routed to other areas of the brain, if at all, after a number of filters have been applied to the visual signal, such as those responsible for line and shape extraction, those that divide the color information into three channels (red/green, blue/yellow, and black/white), and those that divide static from motion information. Thus, any attempt to influence a part of the brain other than the occipital cortex itself will be a hit and miss affair.
A method that has a more global effect on the brain is electro-convulsive therapy (ECT). ECT is achieved by applying a controlled current to the patient""s skull for a period of 1-10 seconds, and is chiefly used in treatment of refractory depression. In recent years, ECT has been made much more safe than previously, although as U.S. Pat. No. 5,769,778, to Abrams et al. describes, it still suffers from a number of side effects, including burns to the scalp and skin and unwanted effects of the induced seizure, including memory loss. Furthermore, because the signal strength must be large enough to penetrate the skull, its effect on the rest of the brain is indiscriminate. It cannot be localized to change activity in certain parts of the brain without affecting others.
Abrams also argues that transcranial magnetic stimulation (TMS) is both a less dangerous and more controlled way of stimulating the brain. U.S. Pat. No. 4,940,453, to Cadwell, describes the type of magnetic coil used in TMS. The ability to produce a localized magnetic field, which in turn triggers localized electrical activity in the brain, has enabled TMS to be successful in the treatment of depression. Reduced activity in the left prefrontal cortex has been implicated in depression, and TMS may work by restoring activity in this area to normal levels. One problem with TMS is that high frequency stimulation may induce seizures. U.S. Pat. No. 5,769,778 describes a method of monitoring the EEG signal in order to prevent such seizures. When incipient features of a seizure are detected, the treatment is halted. Thus, the ""778 patent describes a kind of limited feedback system, albeit one for preventing the adverse effects of TMS treatment, rather than one that attempts to improve the delivery of such.
Even though the aforementioned techniques have allowed some degree of alteration of brain signals incorporating the EEG signal as an indicator, there still exists a need for a system with a continuous feedback mechanism for monitoring and altering brain signals to treat certain diseases and conditions.
The present invention comprises a method and device for producing a desired brain state in an individual. In its most general form, the method of the present invention comprises measuring the activity of the brain, analyzing the measured activity by comparing it to a desired brain activity, and directing one or more magnets to produce magnetic fields which will close the gap between the actual and desired brain state.
In its most general form, the device of the present invention comprises means for measuring the activity of the brain, a computational system for analyzing the measured activity by comparing it to a desired brain activity, and means for directing one or more magnets to produce magnetic fields which will close the gap between the actual and desired brain state.
In one embodiment of the invention, brain activity is revealed by the EEG signal, as measured with multiple electrodes on the surface of the skull. In another embodiment, brain activity is measured with magnetoencephalography (MEG), which is able to detect the weak magnetic fields emanating from the brain. In yet another embodiment, brain activity is measured by functional magnetic resonance imaging (fMRI), which measures blood flow in the brain and from which activity may be inferred.
In one embodiment, the computational system determines the single parameter (the parameters comprise spatial position, pulse strength, pulse frequency, and pulse duration for each magnet) controlling the magnets that most reduces the gap between the actual and desired brain state and alters this parameter accordingly. In another embodiment of the computational system, multiple parameters are altered simultaneously to reduce the gap between the actual and the desired brain states more efficiently. In another embodiment of the computational system, a subset of parameters are chosen for consideration based on a priori knowledge or based on experimentation. In yet another embodiment of the computational system, the mean magnitude of the changes to the parameters is reduced with time so that an approximate solution may be found first and fine tuned later. In a further computational embodiment, a random jump in the values of the parameters is effected if the current set of values is not yielding good results.
In one embodiment of the present invention, multiple magnets are used to produce magnetic fields to stimulate the brain and, optionally, each magnet may be positioned independently on the surface of the skull.
In an embodiment of the present invention, the device comprises electrodes for measuring the EEG signal; an amplifier for amplifying the EEG signal; a converter for converting the measured analog EEG signal into a digital signal; magnets for applying the magnetic field to the brain of the individual; and a positioning apparatus for controlling the position of the magnets on the skull of the individual.
In a further embodiment of the present invention, two magnets are used to treat depression, one exciting the left prefrontal cortex, and one inhibiting the right prefrontal cortex.
In another embodiment of the present invention, multiple magnets are used to induce relaxation by increasing the magnitude of the alpha rhythm and by increasing synchronization between the left and right hemispheres.
In the most general embodiment of the system, an arbitrary psychological state with a known correlated activity state as revealed by EEG, magnetoencephalography (MEG), or functional MRI may be achievable.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.